NCERT Solution for Class Tenth Science Chapter 2
Acids, Bases and Salts
Intext Questions
Page No-17
Questions No-5
Write an equation to show the reaction between Plaster of Paris and water.
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The reaction between Plaster of Paris (CaSO₄ . 1/2 H₂O) and water involves the rehydration of Plaster of Paris to form Gypsum (CaSO₄ . 2H₂O). The chemical equation for this reaction is:
CaSO₄ . 1/2 H₂O + 3/2H₂O →CaSO₄ . 2H₂O
This equation represents the addition of water molecules to Plaster of Paris, resulting in the formation of Gypsum, which is a hydrated calcium sulfate compound. The reaction is exothermic, and during the process, the plaster solidifies as it returns to its original state of Gypsum.
The chemical equation when Plaster of Paris and water reacts:
𝐶𝑎𝑆𝑂₄.1/2𝐻2𝑂+3/2H₂ 𝑂 → 𝐶𝑎𝑆𝑂₄.2𝐻₂𝑂
Plaster of Paris is a white powder and on mixing with water, it changes to gypsum giving a hard solid mass.
𝐶𝑎𝑆𝑂₄.1/2𝐻2𝑂+3/2H₂ 𝑂 → 𝐶𝑎𝑆𝑂₄.2𝐻₂𝑂